import React, { Component } from 'react'
import './index.css'

// 创建 Context对象
const MyContext = React.createContext()
const { Provider, Consumer} = MyContext

export default class A extends Component {

  state = { username: 'tom', age: 18}

  render() {
    const { username, age } = this.state
    return (
      <div className="parent">
        <h3>我是A组件</h3>
        <h4>我的用户名是：{username}</h4>
        <Provider value={{username, age}}>
          <B/>
        </Provider>
      </div>
    )
  }
}

class B extends Component {
  render () {
    return (
      <div className="child">
        <h3>我是B组件</h3>
        <C/>
      </div>
    )
  }
}

// class C extends Component {

//   // 声明接收 Context
//   static contextType = MyContext

//   render () {
//     const { username, age } = this.context
//     return (
//       <div className="grand">
//         <h3>我是C组件</h3>
//         <h4>我从A组件接收到的用户名：{username}, 年龄是{age}</h4>
//       </div>
//     )
//   }
// }

function C () {
  return (
    <div className="grand">
      <h3>我是C组件</h3>
      <h4>我从A组件接收到的用户名：
        <Consumer>
          {value => `${value.username}, 年龄是${value.age}`}
        </Consumer>
      </h4>
    </div>
  )
}